Squadron of Khund warriors reduced in size by Imskian shrink-ray.

Aliens from far far away, and from planet that might be not in our plane of existence.

Siamese twins and acrobats whose skills are so great that they can perform their tricks without ever moving.

An underground group of Russian mutants.

A team of Mel Blanc enthusiasts living in the shattered remains of Pittsburgh.

People with superpowers who don't want to be either superheros or supervillians.

A group of mime themed villians. Who is led by Jessica Mime

Four spirits (Wind, Fire, Blood and Death) that followed the Coyote Kid around. After he died, he became their fifth member, Pain.

The Sidri, also known as Sidrian Hunters, are a hive minded techno-organic alien race and adversaries of the X-Men.

An alien race in The Manhattan Projects.

Protector of the Jungle Paradise in Black Orchid.

They are a crime syndicate of Hawaii. They pride themselves on fighting on equal terms. If the law carries knives they fight with knives. If the law carries guns they will carry guns. When Superboy came to Hawaii they also raised the stakes.

A criminal organization based out of Platinum Flats who have repeatedly gone head-to-head with the Birds of Prey. Also known as the Metahuman Mafia they hide behind a consortium of companies.

Terrorist organization form by former SHIELD Agents on Earth 65.

The Silver Centurions are a conglomerate of heroes from the 43rd century. They have recruited the Silver Agent and have given him his powers.

Cartoon turned comicbook that attempted to follow the success of ThunderCats. A 65 episode run, allowed for a six book comics series spin-off.

A specialist group of monster hunters for The Order of St. George.

12 beings bestowed the power of the Silver Surfer

The Silver Squad consisted of Ripster, Slambeaux and Purdy Larry. They were android bounty hunters formed by Silvermane to terminate Spider Man.

An ancient race of lizard men who are warriors and slavers.

The Sinestro Corps is a mirror organization to the Green Lantern Corps. Its members are chosen from those who can instill great fear and are given Qwardian Yellow Power rings. They are considered to be the evil equivalent of the Green Lantern Corps.

Singularity Investigations is run by Damian Tryp.

The Sinister Six is the name of various teams assembled with the purpose of defeating Spider-Man or pursuing criminal endeavors. Formed and recurrently led by Doctor Octopus, subsequent iterations of the Sinister Six have also been led by Hobgoblin, Sandman, Green Goblin and currently Boomerang.

Amalgam version of the Sinister Six and the Secret Society of Super-Villains

The Sinister Squadron is a Multiversal syndicate of Spider-Man villains lead by a Goblin-ized variant of Gwen Stacy who were hired by an as of yet unknown benefactor to capture Miguel O'Hara, Miles Morales and the Gwen Stacy of Earth-65.

Originally, they were a team of mercenaries and assassins, organized by the original Beetle, Abe Jenkins. Later, the name (minus Sinister) was revitalized by Janice Lincoln (also going by the Beetle) for her female-only crime organization.

Alien race in The Manhattan Projects.

Aquatic creatures from Filipino folklore.

Dangerous and beautiful creatures, portrayed as femmes fatales who lured nearby sailors with their enchanting music and voices to shipwreck on the rocky coast of their island.

The Siren Sect is a group of all female vampires, led by Alyssa.

The Siris are a tentacled alien race of the Marvel Universe.

Female Badoon`s who crave peace and hate all the males of their race .

The planet Feminax was home to the Sisterhood of Evil, the worst female criminals from across the universe. They sought to corrupt Supergirl and turn her into a weapon against Earth.

A group of super-powered female villains founded and led by Madelyne Pryor. Each member was offered the chance to have a dead loved one brought back to life in exchange for their services.

A community was created for minor practitioners to improve their craft.

A splinter secret society that is in constant battle with their previous organization, The Spider Society.

The Sisters of Balance are three mysterious entities with the duty to enforce the Law of Balance

Leaders of a religious cult founded by Mother Night.